1. Field of the Invention
The invention relates to a process for the production of metal oxide powders by spray pyrolysis. The invention relates further to a metal oxide powder obtainable by this process, and to the use thereof.
2. Description of the Background
It is known from EP-A-1142830 to obtain metal oxide powders by burning an aerosol composed of organic precursors dissolved in organic solvents. The aerosol can have a mean drop size of from <1 to 500 μm. A metal oxide powder so produced has a BET surface area of from 1 to 600 m2/g. A disadvantage, however, is that the metal oxide powders often have a wide primary particle size distribution. Furthermore, the examples given, in which only small amounts of product are obtained, cannot be transferred to larger amounts.
WO2004/005184A1 claims a process for the production of metal oxides in which droplets are produced from a solution and are oxidised in a flame. The solution contains at least one starting material and at least 60%, based on the solution as a whole, of a carboxylic acid as solvent. The mean droplet size is from 0.1 to 100 μm, preference being given to smaller droplets. The process has the disadvantage that it is not suitable for the production of relatively large amounts.
A process for the production of cerium oxide is known from WO01/36332A1. This process claims the burning of an aerosol of a cerium oxide precursor in a high-temperature zone of from 700 to 1100° K, wherein the drop size of the aerosol must be smaller than 100 μm. There is nothing in the description of the application relating to the effect of the drop size, nor are values for the droplet size mentioned in the examples. In addition, this process yields inhomogeneous cerium oxide particles of different sizes.